Structure of the Skin Tackmann A & P

Layers of the Skin Epidermis Dermis Subcutaneous Tissue

Epidermis Keratinized – has become hard and tough 5 Zones Stratum Corneum – 20 to 30 cells deep (dead cells filled with keratin) Stratum Lucidum – only on palms and soles of feet Stratum Granulosum Stratum Spinosum Stratum Basale Mitosis!!!!!! Nourishment rich

Epidermis Elevator System Cells move upward replacing the layer above them Totally new epidermis “skin” every 25-45 days!!!

Stratum Corneum Stratum Lucidum Stratum Granulosum Stratum Spinosum Stratum Basale

Melanin and Melanocytes Pigment that ranges from yellow to black Produced by “Melanocytes” Found in stratum basale layer

Melanin and Melanocytes Sunlight stimulates melanocytes Stratum basale cells phagocytize (eat) the secreted melanin Melanin then protects the cell from sunlight Shields the DNA Too much UV will damage the DNA – Causes skin cancer Freckles and Moles Concentrated melanin

Dermis Two Regions Papillary Layer Reticular Layer

Papillary Layer Upper region of the dermis Dermal Papillae Upward projections that indent into the epidermis

Dermal Papillae Contain capillary loops to supply nutrition to the stratum basale Contain Meissner Corpuscles Sensory nerve endings Sense pain

Dermal Papillae Looping patterns of papillae on feet and hands Increases gripping ability in these regions Genetically determined Results in your personal unique fingerprint

Reticular Layer Deepest skin layer Contains Blood vessels Sweat glands Oil Glands Pacinian Corpuscles Sensory neurons that sense pressure

Reticular Layer Abundant with phagocytes Special cells eliminate bacteria that sneak through the epidermis

General Characteristics of the Dermis Rich with Collagen and Elastic Fibers Collagen = toughens and hydrates the skin Elastic = provides skin with elasticity

Appendages Glands Sebaceous and Sweat Hair Nails

Cutaneous Glands Two Groups Sebaceous Glands Sweat Glands Eccrine Glands Apocrine Glands

Sebaceous Glands Location Ducts empty into hair follicle All over body NOT on palms and soles of feet Ducts empty into hair follicle Sometimes directly onto the skin too

Sebaceous Glands Create Sebum Natural lubricant made of oil and fragmented cells Keeps skin soft/moist Prevents brittle hair Chemicals that kill bacteria VERY active during puberty

Blocked Sebaceous Gland If gland gets blocked by Sebum Whitehead Forms If it oxidizes and dries it darkens and forms a Blackhead

Sweat Glands Two Types: Eccrine Glands Apocrine Glands

Eccrine Sweat Glands Location: Produce Sweat Acidic (4 – 6 pH) Entire body Produce Sweat Made of… Water NaCl Vit. C Ammonia, Urea, Uric Acid Acidic (4 – 6 pH) Prevents bacteria growth

Apocrine Sweat Glands Location: Empty into hair follicles Made of… Axillary/Genital regions Empty into hair follicles Made of… Eccrine Sweat sections plus… Fatty Acids & Proteins Milky/Yellowish color Bacteria grow here!!!

Hair and Hair Follicles Protective Functions Head – bumps Eyelashes – protect eyes Nose hairs – filter Many more…..

Hair Anatomy Root Shaft Hair Bulb Matrix Part of the hair enclosed in the follicle Shaft Part of the hair projecting from the skin Hair Bulb Matrix Division of stratum basal cells in the “growth zone” As cells move up and away they die and karatinize

Hair Shaft Shape Oval Shape Flat and Ribbon like Round Smooth, silky, Long and Wavy hair Flat and Ribbon like Curly or Kinky hair Round Straight and coarse

Hair Color Melanocytes found in the hair bulb Various shades of melanin secreted

Hair Follicles (page 100) Inner epidermal sheath Outer Dermal sheath Forms the hair Outer Dermal sheath Supplies blood vessels to the epidermal layer Supports the epidermal layer

Arrector Pili Connects hair follicle to dermal tissue Contracts and pulls hair to stand on end Cold Temps or Frightening situations

Nails Purpose??? Protects distal phalanges Tool for cutting/scraping Enhances sensitivity with touch and movement with the tips of our fingers/toes

Nails Made of Keratin Nail Matrix Growth zone Makes the nail plate Same as horns and hooves Nail Matrix Growth zone Makes the nail plate Rate of 3mm a month

Nail Bed Two Layers Epidermis moves with the nail plate Epidermis